The present invention pertains to a theft prevention device on drive installations on a boat. Many drive installations in a boat involve either an outboard motor or in inboard motor. The present device is directed to an inboard installation. In an inboard installation, the motor is mounted within the boat hull in a substantially linear alignment with the boat hull. The motor has a drive shaft extending to the rear of the boat and ends behind the transom of the boat. The drive shaft has a bevel gear which will mesh with the bevel gear of a downward shaft and then to the propeller gear so as to divert the drive of the motor to a different direction that is downwardly and then outwardly below the water line. This gearing is contained in one unit and is known as the drive of the boat and this particular drive is prone to theft because it is mounted behind the transom of the boat on a housing which contains the drive shaft and can easily be removed from the housing just by removing a few bolts. The bolts include at at least six bolts having nuts thereon. The bolts are arranged on each side of the drive in a certain pattern. Four bolts are arranged at an upper section of the drive with two bolts each being placed on each side of the drive in a parallel pattern. The remaining two bolts of the six bolts are arranged at a lower section of the drive with one bolt each on each side of the drive. These bolts or the nuts thereon are readily visible and available to a prospective felon trying to steal the drive from the motor of the boat by simply removing the above noted bolts and nuts. Insurance companies are well aware of this weakness in the mounting of motor and drive mounts in a motor boat and would greatly appreciate any device that would prevent the above noted theft.